Ch. Fetal Central Nervous System Flashcards
The neural tube should be closed by how many weeks?
6 menstrual weeks
Which imaging plane is best to detect spina bifida?
The transverse plane
The sagittal and or coronal plane is used to assess what aspects of the spine?
Cervical and lumbosacral curvatures
sacral caudal tapering
configuration of vertebral ossification centers
The sagittal and or coronal plane is used to assess what aspects of the spine?
Cervical and lumbosacral curvatures
sacral caudal tapering
configuration of vertebral ossification centers
What is the normal limit of the lateral ventricles throughout all of the gestational age?
<10 mm
What is the normal range of measurements for the cisterna magna throughout all of gestational age?
> 3mm and <10mm
What kind of defects occur when there is a failure of the neural tube to completely close by 6 weeks?
Neural tube defects (NTDs)
What is known to decrease a patient’s risk of NTDs?
Folic acid
The most common NTD, occurring more common in females and multiple gestations, it is the congenital absence of the cerebral hemispheres and cranial vault
Anencephaly
Sonographic appearance of anencephaly
“Frog face” sign
absence of the cerebral hemispheres and cranial vault
face and orbits are present
fetal cranium should be present by 12 weeks (15 weeks at the latest)
POLYHYDRAMNIOS (due to ineffective swallowing)
Developmental abnormality in which the cranium is partially or completely absent with the development of abnormal brain tissue, will have elevated levels of MSAFP.
Acrania aka exencephaly
Sono finds of acrania/ exencephaly
Break in the skull with the presence of large amount of brain tissue
reliably demonstrated by 16 weeks as lack of ossified cranium
The herniation of brain and meninges or meninges and CSF (meningocele) through a cranial defect
Encephalocele aka Cephalocele
Where are encephaloceles usually located
Midline, most commonly occipital, may be frontal or lateral
Encephaloceles are associated with what syndrome
Meckel-Gruber syndrome
Sono finds of encephalocele
purely cystic extracranial mass (meningocele)
solid mass contiguous with the cranium (cephalocele)
often associated with hydrocephalus and polyhydramnios
Break in the skull??
Term for lack of closure of the vertebral column, usually occurring in the lumbosacral region
Spina bifida
Herniation of the meninges and CSF through a spinal defect
meningocele
herniation of the meninges AND neural elements (spinal cord) through the spinal defect
Meningomyelocele
Transverse sono finds of spina bifida
Splaying of the posterior elements into a “U” or “V” configuration
when sac is intact, cystic structure may be seen extending from the back
Sagittal sono finds of spina bifida
Splaying of the parallel ossification centers
soft tissue defect or discontinuity or skin and muscle of posterior back
(be aware of normal widening of the spine in the cervical and lumbar regions)
Associated findings in spina bifida are secondary to the —— (what syndrome or condition)
Arnold-Chiari II M=malformation
Intracranial signs of spina bifida
“Lemon” sign - flattening of the temporal/frontal bones due to decreased intracranial pressure
“Banana” sign - obliteration of cisterna magna by abnormal configuration of the cerebellum
hydrocephalus - Lat vent > 10 mm
Rare malformation in which the occiput is fused to the cervical region.
Iniencephaly
Sono finds of Iniencephaly
occipital encephalocele
cervical spina bifida
marked head and neck hyperextension
Associated intracranial findings in spina bifida are secondary to what malformation?
Arnold-Chiari II Malformation
Describe the flow of CSF starting with the 1st and 2nd ventricles
1) lateral ventricles
2) Foramen of Monro aka Intraventricular foramen
3) Third ventricle
4) Aqueduct of Sylvius aka Cerebral Aqueduct
5) Fourth ventricle
6) fluid will drain into either the Foramen of Luschka or the Foramen of Magendie
Dilatation of the ventricular system secondary to an increase in the volume of CSF OR the decrease in absorption
Ventriculomegaly aka Hydrocephalus
What is the most common cause of OBSTRUCTIVE or NONCOMMUNICATING hydrocephalus?
Aqueductal stenosis
Define communicating hydrocephalus
There is dilation of all ventricles and the subarachnoid space caused by faulty absorption of CSF or increased CSF production. NOT CAUSED BY AN OBSTRUCTION
Describe sonographic findings of hydrocephalus
the presence of excess fluid in the lateral ventricles causing them to measure >10 mm
“DANGLING” choroid plexus
Measurements of ventriculomegaly/ hydrocephalus
Mild ventriculomegaly - 10-12 mm
Moderate Ventriculomegaly - 12.1-15 mm
Severe ventriculomegaly/ Hydrocephalus >15 mm
A spectrum of disorders resulting from absent or incomplete diverticulation (division) of the prosencephalon (forebrain) into the cerebral hemispheres and lat vents
Holoprosencephaly
Which trisomy is associated mostly with holoprosencephaly
Trisomy 13 aka Patau syndrome
What type of facial anomalies are seen with holoprosencephaly
Cyclopsia (single orbit)
Proboscis
Hyportelorism
Facial clefts
Type of holopros that is the least severe, associated with normal separation of the thalami, hemispheres, and ventricles. There is an absent CSP and olfactory tracts
Lobar holoprosencephaly
Type of holopros that is associated with partial separation of ventricles and hemispheres with occipital lobe present. There is an incomplete fused thalami
Semi-lobar holoprosencephaly
The most severe form of holopros in which there is a MONOVENTRICLE, fused thalami, and absence of the falx cerebri
Alobar holoprosencephaly
T or F, in the presence of holoprosencephaly, the cerebellum and posterior fossa will be normal
True. It is the prosencephalon (forebrain) that is affected by holopros, not the posterior portion of the brain
CNS disorder that is characterized by near total lack of the cerebral hemispheres with intact and normally developed meninges and skull
Hydranencephaly
What is hydranencephaly thought to be caused by
Bilateral internal carotid artery occlusion or malformation
Sono finds of hydranencephaly
Macrocephaly
absent cerebral tissue (cortical mantle)
Falx cerebri is present
Normal midbrain and basal ganglia
Polyhydramnios
CNS disorder that is defined as the complete or partial absence of the cerebellar vermis and posterior fossa cystic dilatation communicating with the 4th ventricle
Dandy walker malformation (DWM)
List things that DWM has been associated with
Autosomal recessive syndromes
maternal infection
Diabetes
exposure to alcohol
Sono finds of dandy walker malformation
complete or partial agenesis of the vermis with flattened cerebellar hemispheres
large midline cystic structure in posterior fossa
associated with ventriculomegaly and poly
diff from subarachnoid cysts by contiguity with 4th vent
Development of the corpus callosum should be complete at
20 weeks
Sono finds of agenesis of the corpus callosum
ABSENT CSP
elevated dilated third ventricle
“TEAR DROPPED” shaped ventricles
Moosehead appearance on MRI
Well defined cystic structure superior and posterior to the thalamus with turbulent and or arterial flow
Vein of Galen aneurysm
Choroid plexus cysts are associated with which trisomy
Trisomy 18 aka Edwards syndrome
What brain tumors are the most common
teratomas
Condition in which the brain lacks sulci and gyri resulting in an overall smooth apperance
Lissencephaly
Condition characterized by clefts in the cerebral hemispheres in the region of the primary fissures
Schizencephaly ( the brain will appear split into anterior and posterior parts)
Simple cystic structures WITHIN brain parenchyma that communicate with the ventricular system
Porencephaly
A rare tumor arising from the embryonic cells of the sacrum/coccyx, they may be external, intrapelvic, and or intra-abdominal
Sacrococcygeal teratoma
Sono finds of sacrococcygeal teratomas
an internal or external complex large mass
poly
increased AFP
possible hydrops fetalis
What maternal condition is associated 16% with caudal regression syndrome
Diabetes mellitus
What is caudal regression syndrome
Includes a spectrum of skeletal anomalies of the lower spine and lower limbs such as sacral agenesis, lumbar spine, or even lower thoracic agenesis. THE ABSENCE OF THE SPINE, it just stops forming
Abnormal curvature of the spine may involve any segment but is most frequently found in which region
Thoracolumbar region
